To advance neurological gene therapy applications into the clinic there is an urgent need to improve our understanding of gene delivery vectors, with particular emphasis on distribution and safety after direct brain delivery. While AAV2 currently dominates clinical development, alternative AAV serotypes may be better suited for some applications. The recent game-changing development of image-guided delivery techniques provides opportunity to accurately compare different vectors after direct brain delivery. Accordingly we aim to investigate the distribution and immune responses of 5 AAV serotypes (AAV1, 2, 5, 8 and 9) after confined delivery to grey or white matter structures in the non-human primate (NHP) brain. This in-depth assessment of AAV vectors will provide investigators with scientific rational for selecting a specific vector for a particular neurological application.